Forest Fires and Satellite Imagery

The beginning of October marks the beginning of the fall fire weather season in east Kentucky, which lasts through the middle of December. In general, drier weather is common in the fall months in east Kentucky and as a result many small "fuels" are present for fires to burn. What do we mean by "fuels"? Fall brings the changing of leaves, in which they dry up and die. This creates litter on a forest floor and the drier this litter becomes the more flammable it gets. Obviously, the more litter there is, the more "fuel" there is for a fire to burn. Fuels are broken up into different categories based on their size. Surface fuels such as small twigs and sticks are less than a half an inch in diameter and are called 10 hour fuels. These are fuels that can dry out quickly because of their small size. Since most of these fuels stay near the forest floor, fires that are burning these types of fuels generally do not spread to the higher tree tops. Larger fuels (100 hour), such as small limbs, are considered to be 1 to 3 inches in diameter and take longer to dry out before they can be burned. Still larger fuels (1,000 hour) of 3 to 8 inches in diameter take even longer to dry out. Basically, after a decent rainfall, low hour fuels (1 or 10 hour fuels) dry out quickly with the larger hour fuels (1,000 hour) taking longer to dry out. After a prolonged dry period, there are more fuels and larger fuels to burn. This results in different types of forest fires being possible, including fires that stretch from the forest floor to the tree tops. There are three main types of fires with regard to the vertical structure of a forest. The first is a ground fire that burns the humus layer of a forest and stays below the surface. This humus layer is made up of decomposing substances within the soil layer and includes roots. The second type of fire is a surface fire in which leaves, twigs, sticks, pine needles, and bushes might be burned. These are where the low hour fuels come in. The last type of fire, and likely the most dangerous, is called a crown fire. This is where the fire spreads to tree tops and can spread quickly, especially with dry, windy conditions. It is not uncommon for two or more of these types of fires to be burning at once. Source: (Bureau of Land Management)

Sometimes, if forest fires become large enough, they can be detected by satellite imagery. In the image below you can see several small fires depicted by red dots in east Kentucky and West Virginia. Some smoke is evident in the atmosphere as well, which is depicted by the very light blue streaks near the fires. Also some regular clouds are evident as the bright light blue colors in central Kentucky and Tennessee and northern West Virginia. Many times, fires of this size are actually prescribed burns by the forest service and national parks. These prescribed fires are designed to prevent future "wildfires" and are also beneficial to forest ecosystems in the long run.

Credit: NOAA

The image below is of larger forest fires in central Idaho and western Montana. These fires are much more evident due to larger areas of red and have much more pronounced smoke plumes. Most fires of this size are considered "wildfires" as they are not prescribed or planned. Sometimes it takes weeks to months to get "wildfires" under control and many homes and businesses can be endangered. Weather conditions that are most favorable for continued "wildfire" behavior are characterized by a dry and windy airmass.

Credit: NOAA

The image below is an example of what a smoke plume looks like. A plume this size appears pretty small and would have to be much larger and more intense to look like the Idaho and Montana plumes do in the picture above.